Robotics has come to denote the implementation of human like activities by machines. This includes robots which have the capability of handling materials analogous to handling by the human appendages, including arms and hands. The robot can be controlled to act according to the operator's direction or by the use of a pre-established program to carry out many mechanical functions that substitute for a human, particularly in environments which are hostile to humans. Outer space is one such hostile environment; extremely cold and in vacuum in which a human could not survive without suitable protection. On Earth hostile environments also exist where a person would be subjected to the ill effects of extreme heat or cold, nuclear radiation, toxic chemical waste, etc. Deep-sea underwater exploration also involves working in an extremely hostile environment, where robotic devices could perform many of the tasks performed by humans in a bathysphere. Even more importantly, the robot can carry out manipulative tasks repeatedly and accurately without tiring. A robotic manipulator forms part of the Robot and performs the manipulative functions.
In an article entitled "Study On a Lightweight and Flexible Robot Manipulator", A. Hemami, Robotics 1 (1985), pages 27 through 36, the subject of a flexible robotic arm, one that can assume a large number of shapes and end positions, is addressed. In the article, sketches of a flexible snake like arm design are presented. The arm contains numerous sections or joints joined together by a bellows like flexible support skin that contains the requisite amount of strength and flexibility to support the sections that the author required. A series of disks border each joint and each disk contains centrally located triangular shaped openings. The disks are supported by the flexible sheath skin that both covers internal elements and is an important part of the structures support. At least three strings are attached to spaced locations on each disk and extend through the triangular shaped passage to the rear of the arm.
Hemami intends for each section to be manipulated remotely by positioning or tugging of the strings, much like a puppeteer controls a puppet's arms and legs. However, unlike manipulating a puppet, in the suggested manipulator structure, movement of any one joint section appears to have an effect on string tension employed in connection with the other sections of the arm. In a theoretical analysis, Hemami notes a number of positions which the proposed structure cannot achieve; limitations that are inherent in the approach of a combination flexible skin and string type control arrangement. Although recognizing the desirability of a flexible robotic arm, the design addressed in the article does not appear to achieve a practical structure for satisfying that end.
The present invention achieves a practical and operative multi-section robotic arm that is capable of being positioned over no less than a hemisphere of three dimensional locations; does not rely upon and is not limited by the characteristics of a bellows like support skin and is not limited by and does not require use of complicated tensioned string control arrangements, even though the present invention can also use strings as actuators, if necessary.
The subject of manipulators is also partially addressed by Lambert in U.S. Pat. No. 4,651,589 granted Mar. 24, 1987 for a polyarticulated retractile mechanism. In the Lambert patent a mechanism is formed of elemental units each containing two spaced plates supported at at least three locations on each plate by foldable support arms extending between the two plates. In one device the arms contain end and intermediate ball and socket joints and a hinge connection at the bottom arm end so as to be foldable outwardly of the plate.
In a second embodiment illustrated in the Lambert patent the support arms are hinged at each end and contain an intermediate ball and socket joint and are foldable outwardly at the plate. One of the arms is intended to be driven by an actuator which is a servo controlled motor. This positions the two plates relative to one another. As shown in Lambert the support arms extend outside the area defined by the top and bottom plates. The exact nature of the control and mode of operation is not prescribed and although Lambert appears to describe some elements and results that he expects that structure to achieve, the exact operation of the mechanism and scope of the mechanism's capability appear unexplained and left to conjecture.
In Inoue U.S. Pat. No. 4,607,578 granted Aug. 26, 1986 a positioning mechanism is illustrated that supports and positions a table on a base using three complicated pantagraph mechanisms driven by motors. The table is supported at three spaced locations by the arms of the pantagraph mechanisms and may be positioned at any angle. Although the table structure is not a robotic arm, Inoue illustrates further the positional flexibility obtained from three spaced movable supports.
Other patents describe structure generally related to the present subject to which the reader may make reference as desired: U.S. Pat. Nos. 4,393,728 Larson granted July 19, 1983; 4,494,417 Larson granted Jan. 12, 1985; 3,712,481 Harwood granted Jan. 23, 1973; and 4,621,965 Wilcox granted Nov. 11, 1986.
A principal object of the present invention is to provide a robotic manipulator or positioning device, such as a robotic arm, that achieves a large number of shapes and end positions. A further object is to provided a robotic manipulator arm 15 construction that is able to curve or snake around obstructions or complicated contours and which can be held or fixed at that shape. Another object of the invention is to provide a versatile mechanical manipulator capable of use as robotic hands, legs and arms. It is a still further object to provide a positioning device of simple construction that is easily manufactured with interchangeable parts using mass production manufacturing techniques. The robotic arm presented is particularly adapted to control by computer, a decided advantage. A still additional object is to enable building a robotic manipulator that could be applied as an artificial prosthetic leg or arm, complete with fingers, for amputees; with artificial intelligence and coupling directly to neurons in the amputated stub the arm can be controlled entirely by brain function.